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The design, evaluation, and management of immunisation programmes

Communicable Disease Control: Immunisation

This section covers:

  • The design, evaluation, and management of immunisation programmes
  • Choices in developing an immunisation strategy

Immunisation

Aim of immunisation: to provoke immunological memory to protect individual against a particular disease

Two types of immunisation:

  • Passive: temporary protection e.g. Immunoglobulin (Ig's)
  • Active: longer term protection leading to the formation of antibodies

Types of vaccines

Live vaccine (attenuated)

  • Measles Mumps Rubella (MMR), oral polio, Bacille Calmette Guerin (BCG), Yellow Fever
  • single dose
  • long duration of immunity
  • less stable: may revert to a virulent strain
  • can cause disease in immuno-suppressed, (exception is HIV patients where do recommend, apart from BCG)

Inactivated vaccine (killed)

  • Diphtheria Tetanus Pertussis (DTP), typhoid, Hepatitis B, flu, rabies, meningitis C, Hib
  • multiple doses and booster
  • short immunity
  • stable

Contra indications to immunisation

  • very few real contra-indicators
  • severe reaction to previous dose
  • immuno-suppression (no live vaccines)

Vaccine failure

  • primary: individual fails to make adequate immune response to initial vaccination
  • secondary: individual makes initial adequate response, but then immunity wanes over time

Vaccination programmes

Development of a Vaccine Programme

  • Prior to designing a vaccine programme, must establish
    • Is there a need for the programme? - does the disease cause a significant public health problem
    • Is a suitable vaccine available that is safe and effective?

Aim of Immunisation Programme

  • To protect those at highest risk (selective immunisation strategy
    OR
  • To eradicate, eliminate or contain disease (mass immunisation strategy)

Vaccination strategies

A. Selective Vaccination

  • Given to those at increased risk
  • Examples - for travel e.g. Hepatitis A; occupational e.g. Hepatitis B; chronic disease e.g. Splenectomy - meningococcal, Hib; outbreak e.g.Hepatitis A

B. Mass Vaccination

Either

  • Eradication - Disease and its causal agent have been removed worldwide e.g. small pox
  • Elimination - Disease has disappeared from one WHO region but remains elsewhere e.g. polio
  • Containment - The point at which the disease no longer constitutes a 'significant public health problem' e.g. Hib

Issues in Vaccine Policy Decisions

  • Aim of programme
  • Cost of programme
  • Population accessibility
  • Cultural attitudes and practices
  • Facilities available for delivery

The need for a vaccination programme depends on:

  • disease incidence
  • age distribution of disease
  • disease trends
  • disease complications
  • mortality
  • population / cultural attitudes
  • cost and benefit
  • political expenditure
  • vaccine efficacy and side effects
  • availability and validity of delivering
  • provision of trained primary care providers
  • vaccine type

Development of a vaccination programme

Pre-license

Phase 1 studies

safety studies - in healthy adults

Phase 2 studies

immunogenicity - in target population (100-120)

Phase 3 studies

protective efficacy - in target population (large)

Post-license

Phase 4 studies

surveillance - to detect adverse events

Plus: pharmo-economic studies - Cost Benefit Analysis (CBA) / Cost Effective Analysis (CEA) (at phase 3)

Implementation of a vaccination policy

  • choice of policy - mass or selective
  • publish recommendations ('green book': Immunisation Against Infectious Disease)
  • license vaccine
  • purchase vaccine
  • Then, media campaign and start giving vaccinations

Factors associated with low immunisation coverage

  1. socio-demographic variables
    • deprived, inner city living
    • mobile families
    • birth order, large families
    • children with chronic illnesses
    • ethnicity
  2. personal variables
    • parents
    • professionals
  3. health service variables - generally good in the UK, but be aware of some limitations
    • poor co-ordination (private and public sectors)
    • unclear responses
    • access to guidelines and policies

UK initiatives leading to improved coverage in 1990s

  • 1986: district immunisation co-ordinator appointed
  • 1987: rapid monitoring and feedback of coverage data - COVER statistics
  • 1988: national guidelines on immunisation
  • 1990: accelerated immunity schedule
  • 1990: GP contracts - financial incentives
  • 1992: parent-held records
  • national vaccination campaigns - intermittent (e.g. MMR/Hib)
  • other:
    • opportunistic delivery
    • specific immunisation clinics
    • targeted information campaigns

    UK immunisation service is consider a world example

  • initiated by birth notification on 'Child Health System'
  • Community Health Service (CHS) computer generates automatic letters inviting children for vaccination, and ensures GP call and recall for immunisation

Vaccine Coverage

COVER (Cover of Vaccination Evaluated Rapidly)

  • Since 1988 computerised child health records contain vaccination details of all resident children. These are completed each time a vaccine is given by a healthcare professional
  • Every 3 months information is collated from these child health systems to identify the number of children who have completed vaccine courses at 1, 2 and 5 years of age and fed to the HPA
  • The data is fed back to local healthcare workers, immunisation co-ordinators and the PCT to improve coverage

Uses

  • Detect change rapidly and monitor trends in uptake
  • Look for pockets of poor coverage
  • Estimate vaccine efficacy
  • Measure impact and success of a vaccination campaign

Evaluation of Vaccine Programmes

  • Disease incidence
  • Susceptibility
  • Vaccine Coverage
  • adverse events and vaccine safety

Monitoring Adverse Events and Vaccine Safety

  • Committee on Safety of Medicines (CSM) advises the Medicines and Healthcare products Regulatory Agency (MHRA) on safety, quality and efficacy of vaccines
  • MHRA responsible for Yellow Card Adverse Drug Reaction reporting system
  • Yellow Card reports can signal possibility that a product may be associated with certain risks. These can then be investigated further to decide whether a side effect is truly from a vaccine or not

United Kingdom childhood vaccination schedule 2006

All children starting the immunisation programme at 2 months of age will follow the schedule below.

When to immunise

What is given

Vaccine and how it is given

Two months old

Diphtheria, tetanus, pertussis, polio and Haemophilus influenzae type b (DTaP/IPV/Hib)

One injection (Pediacel)

Pneumococcal (PCV)

One injection (Prevenar)

Three months old

Diphtheria, tetanus, pertussis, polio and Haemophilus influenzae type b (DTaP/IPV/Hib)

One injection (Pediacel)

Meningitis C (MenC)

One injection (Neisvac C or Meningitec)

Four months old

Diphtheria, tetanus, pertussis, polio and Haemophilus influenzae type b (DTaP/IPV/Hib)

One injection (Pediacel)

Pneumococcal (PCV)

One injection (Prevenar)

Meningitis C (MenC)

One injection (Neisvac C or Meningitec)

Around 12 months

Haemophilus influenzae type b, Meningitis C (Hib/MenC)

One injection (Menitorix)

Around 13 months

Measles, mumps and rubella (MMR)

One injection (Priorix or MMR II)

Pneumococcal (PCV)

One injection (Prevenar)

Three years four months to five years old

Diphtheria, tetanus, pertussis and polio (dTaP/IPV or DTaP/IPV)

One injection (Repevax or Infanrix-IPV)

Measles, mumps and rubella (MMR)

One injection (Priorix or MMR II)

Thirteen to 18 years old

Tetanus, diphtheria and polio (Td/IPV)

One injection (Revaxis)

 

© Sarah Anderson, Gayatri Manikkavasagan 2008